Performance of biodegradable microcapsules of poly(butylene succinate), poly(butylene succinate-co-adipate) and poly(butylene terephthalate-co-adipate) as drug encapsulation systems

Microcapsules of Poly(butylene adipate-co-terephthalate) (PBAT) Loaded with Aliphatic Isocyanates for Adhesive Applications

This work introduces the encapsulation of hexamethylene diisocyanate derivatives (HDI, TriHDI, and PHDI) with the biodegradable polymer poly(butylene adipate-co-terephthalate) (PBAT) through a solvent evaporation method. These microcapsules (MCs) were then employed in adhesive formulations for footwear. Moreover, MCs containing PHDI were produced in a closed vessel, demonstrating the potential for recovering and reusing organic solvents for the first time. The MCs were achieved with an isocyanate payload reaching up to 68 wt %, displaying a spherical shape, a core-shell structure, and thin walls without holes or cracks. The application of MCs as cross-linking agents for adhesives was evaluated following industry standards. The adhesives' strength surpassed the minimum requirement by a significant margin. Creep tests demonstrated that the formulation with MCs exhibits superior thermostability. Furthermore, the formulation with MCs-PHDI presented the best results reported to date for this type of system, as no displacement was observed in the bonded substrates. Environmental assessment indicates that adhesives with MCs have higher global warming potential (+16.2%) and energy consumption (+10.8%) than the standard commercial adhesives, but under alternative realistic scenarios, the differences can be insignificant. Therefore, adhesive formulations incorporating MCs promise to be on par with traditional adhesive systems regarding environmental impacts while providing benefits such as improved and safe handling of isocyanates and excellent bonding effectiveness.

Modified Release of the Pineal Hormone Melatonin from Matrix Tablets Containing Poly(L-lactic Acid) and Its PLA-co-PEAd and PLA-co-PBAd Copolymers

In terms of drug delivery, the attractive properties of poly(L-lactic acid) (PLA) and its aliphatic polyesters, poly(ethylene adipate) (PEAd) and poly(butylene adipate) (PBAd), render them ideal co-formulants for the preparation of modified-release pharmaceutical formulations. Furthermore, we have previously demonstrated that by adding a “softer” aliphatic polyester onto the macromolecular chain of PLA, i.e., PEAd or PBAd, resulting in the formation of the PLA’s copolymers (PLA-co-PEAd and PLA-co-PBAd, in 95/5, 90/10, 75/25 and 50/50 weight ratios), the hydrolysis rate is also severely affected, leading to improved dissolution rates of the active pharmaceutical ingredients (API). In the present report, we communicate our findings on the in vitro modified release of the chronobiotic hormone melatonin (MLT), in aqueous media (pH 1.2 and 6.8), from poly(L-lactic acid) and the aforementioned copolymer matrix tablets, enriched with commonly used biopolymers, such as hydroxypropylmethylcellulose (HPMC K15), lactose monohydrate, and sodium alginate. It was found that, depending on the composition and the relevant content of these excipients in the matrix tablets, the release of MLT satisfied the sought targets for fast sleep onset and sleep maintenance. These findings constitute a useful background for pursuing relevant in vivo studies on melatonin in the future.

A Brief Review of Poly (Butylene Succinate) (PBS) and Its Main Copolymers: Synthesis, Blends, Composites, Biodegradability, and Applications

PBS, an acronym for poly (butylene succinate), is an aliphatic polyester that is attracting increasing attention due to the possibility of bio-based production, as well as its balanced properties, enhanced processability, and excellent biodegradability. This brief review has the aim to provide the status concerning the synthesis, production, thermal, morphological and mechanical properties underlying biodegradation ability, and major applications of PBS and its principal copolymers.

Poly(l-Lactic Acid)-co-poly(Butylene Adipate) New Block Copolymers for the Preparation of Drug-Loaded Long Acting Injectable Microparticles

The present study evaluates the use of newly synthesized poly(l-lactic acid)-co-poly(butylene adipate) (PLA/PBAd) block copolymers as microcarriers for the preparation of aripiprazole (ARI)-loaded long acting injectable (LAI) formulations. The effect of various PLA to PBAd ratios (95/5, 90/10, 75/25 and 50/50 w/w) on the enzymatic hydrolysis of the copolymers showed increasing erosion rates by increasing the PBAd content, while cytotoxicity studies revealed non-toxicity for all prepared biomaterials. SEM images showed the formation of well-shaped, spherical MPs with a smooth exterior surface and no particle's agglomeration, while DSC and pXRD data revealed that the presence of PBAd in the copolymers favors the amorphization of ARI. FTIR spectroscopy showed the formation of new ester bonds between the PLA and PBAd parts, while analysis of the MP formulations showed no molecular drug-polyester matrix interactions. In vitro dissolution studies suggested a highly tunable biphasic extended release, for up to 30 days, indicating the potential of the synthesized copolymers to act as promising LAI formulations, which will maintain a continuous therapeutic level for an extended time period. Lastly, several empirical and mechanistic models were also tested, with respect to their ability to fit the experimental release data.

Block copolymers based on poly(butylene adipate) and poly(L-lactic acid) for biomedical applications: synthesis, structure and thermodynamical studies

This work describes the synthesis of poly(butylene adipate) (PBAd), by melt polycondensation, poly(l-lactic acid) (PLLA), by ring opening polymerization, and the new block copolymer PLLA/PBAd in ratios 90/10, 95/5, 75/25 and 50/50. Due to the biocompatibility and low toxicity of neat PBAd and PLLA, these copolymers are suitable to be used in biomedical applications. The 1H and 13C nuclear magnetic resonance spectroscopy techniques were employed for structural characterization. The thermal transitions, with an emphasis on crystallization, were assessed by differential scanning calorimetry, supplemented by X-ray diffraction and polarized optical microscopy. Molecular mobility studies were conducted using two advanced techniques, broadband dielectric spectroscopy and thermally stimulated depolarization currents. The results from the structural techniques, in combination with each other, provided proof of the presence of PLLA and PBAd blocks and, moreover, the successful copolymer synthesis. The overall data showed that the different co-polymer compositions result directly in severe changes in the polymer crystal distribution and, indirectly, the formation of PBAd micro/nano domains surrounded by PLLA. Furthermore, it was demonstrated that both the continuity of the two polymers throughout the copolymer volume and the semicrystalline morphology can be tuned to a wide extent. The latter makes these systems quite promising envisaging biomedical applications, including the encapsulation of small molecules, e.g. drug solutions. The molecular mobility map was constructed for these systems for the first time, revealing the local (short scale) and segmental (larger nm scale) mobility of PBAd and PLLA, as well as intermediate behaviors of the copolymers.

Optimization and Formulation of Fucoxanthin-Loaded Microsphere (F-LM) Using Response Surface Methodology (RSM) and Analysis of Its Fucoxanthin Release Profile

Fucoxanthin has interesting anticancer activity, but is insoluble in water, hindering its use as a drug. Microencapsulation is used as a technique for improving drug delivery. This study aimed to formulate fucoxanthin-loaded microspheres (F-LM) for anticancer treatment of H1299 cancer cell lines and optimize particle size (PS) and encapsulation efficiency (EE). Using response surface methodology (RSM), a face centered central composite design (FCCCD) was designed with three factors: Polyvinylalcohol (PVA), poly(d,l-lactic-co-glycolic acid) (PLGA), and fucoxanthin concentration. F-LM was produced using a modified double-emulsion solvent evaporation method. The F-LM were characterized for release profile, release kinetics, and degradation pattern. Optimal F-LM PS and EE of 9.18 µm and 33.09%, respectively, with good surface morphology, were achieved from a 0.5% (w/v) PVA, 6.0% (w/v) PLGA, 200 µg/mL fucoxanthin formulation at a homogenization speed of 20,500 rpm. PVA concentration was the most significant factor (p < 0.05) affecting PS. Meanwhile, EE was significantly affected by interaction between the three factors: PVA, PLGA, and fucoxanthin. In vitro release curve showed fucoxanthin had a high burst release (38.3%) at the first hour, followed by a sustained release stage reaching (79.1%) within 2 months. Release kinetics followed a diffusion pattern predominantly controlled by the Higuchi model. Biodegradability studies based on surface morphology changes on the surface of the F-LM, show that morphology changed within the first hour, and F-LM completely degraded within 2 months. RSM under FCCCD design improved the difference between the lowest and highest responses, with good correlation between observed and predicted values for PS and EE of F-LM.

Preparation of New Risperidone Depot Microspheres Based on Novel Biocompatible Poly(Alkylene Adipate) Polyesters as Long-Acting Injectable Formulations

Risperidone (RIS)-loaded microspheres based on poly(alkylene adipate)s derived from dicarboxylic acids and different aliphatic diols were prepared by the oil in water emulsion and solvent evaporation method. Specifically, 3 polyesters, namely poly(ethylene adipate), poly(propylene adipate), and poly(butylene adipate), were prepared with the aid of a 2-stage melt-polycondensation method and characterized by gel permeation chromatography, proton nuclear magnetic resonance (¹H NMR), differential scanning calorimetry, and X-ray diffraction analysis. Results showed that the molecular weight of the polyesters increased as the diol molecular weight increased, while all polymers were of semi-crystalline nature and the melting temperature was varying from 49.1°C to 51.8°C and 65.9°C for poly(propylene adipate), poly(ethylene adipate), and poly(butylene adipate), respectively. The particle size of the RIS-loaded microspheres varied from 10 to 100 μm depending on the polyester type and the drug loading, while X-ray diffraction analysis revealed amorphous active pharmaceutical ingredient in the cases of high drug-loaded microspheres. In vitro drug release studies along with scanning electron microscopy images of microspheres after the completion of dissolution process showed that in all cases RIS release was controlled by the glass transition temperature of polyesters and physical state of active pharmaceutical ingredients via diffusion.

Fabrication of Fucoxanthin-Loaded Microsphere(F-LM) By Two Steps Double-Emulsion Solvent Evaporation Method and Characterization of Fucoxanthin before and after Microencapsulation

Microencapsulation is a promising approach in drug delivery to protect the drug from degradation and allow controlled release of the drug in the body. Fucoxanthin-loaded microsphere (F-LM) was fabricated by two step w/o/w double emulsion solvent evaporation method with poly (L-lactic-coglycolic acid) (PLGA) as carrier. The effect of four types of surfactants (PVA, Tween-20, Span-20 and SDS), homogenization speed, and concentration of PLGA polymer and surfactant (PVA), respectively, on particle size and morphology of F-LM were investigated. Among the surfactants tested, PVA showed the best results with smallest particle size (9.18 µm) and a smooth spherical surface. Increasing the homogenization speed resulted in a smaller mean F-LM particle size [d(0.50)] from 17.12 to 9.18 µm. Best particle size results and good morphology were attained at homogenization speed of 20 500 rpm. Meanwhile, increased PLGA concentration from 1.5 to 11.0 (% w/v) resulted in increased F-LM particle size. The mean particle size [d(0.5)] of F-LM increased from 3.93 to 11.88 µm. At 6.0 (% w/v) PLGA, F-LM showed the best structure and external morphology. Finally, increasing PVA concentration from 0.5 to 3.5 (% w/v) resulted in decreased particle size from 9.18 to 4.86 µm. Fucoxanthin characterization before and after microencapsulation was carried out to assess the success of the microencapsulation procedure. Thermo gravimetry analysis (TGA), glass transition (Tg) temperature of F-LM and fucoxanthin measured using DSC, ATR-FTIR and XRD indicated that fucoxanthin was successfully encapsulated into the PLGA matrix, while maintaining the structural and chemical integrity of fucoxanthin.

Intertwining lamellar assembly in porous spherulites composed of two ring-banded poly(ethylene adipate) and poly(butylene adipate)

Poly(1,4-butylene adipate) (PBA) and poly(ethylene adipate) (PEA), each with the ability to form ring-banded morphologies at same Tc, were simultaneously crystallized from mixtures of various compositions. Investigations on morphology, phase and thermal behavior were conducted in order to reveal lamellar packing and spherulitic structures in this binary system. As PBA is faster-crystallizing and dominates the crystallization process, it is relatively easy to maintain its ordered ring-banded pattern in a PBA/PEA blend when there is a moderate amount of PBA in the composition (40 wt% or greater). On the other hand, PEA is much slower crystallizing and it has to be in extreme majority (PEA > 95 wt%) in the PBA/PEA mixtures in order to crystallize into ring-banded spherulites of PEA pattern. When PBA composition is between 10 and 40 wt% in the PBA/PEA blend, simultaneous crystallization of PBA and PEA leads to an interpenetrating morphology with an interwoven bird-nest pattern. Porous structures with crevices, owing to the interpenetrating PBA and PEA lamellae, resulted in simultaneous crystallization of these two biodegradable polyesters.

Current progress on bio-based polymers and their future trends

This article reviews the recent trends, developments, and future applications of bio-based polymers produced from renewable resources. Bio-based polymers are attracting increased attention due to environmental concerns and the realization that global petroleum resources are finite. Bio-based polymers not only replace existing polymers in a number of applications but also provide new combinations of properties for new applications. A range of bio-based polymers are presented in this review, focusing on general methods of production, properties, and commercial applications. The review examines the technological and future challenges discussed in bringing these materials to a wide range of applications, together with potential solutions, as well as discusses the major industry players who are bringing these materials to the market.

Preparation of embolic NEMs loading capecitabine

The nanoparticles-embedded microcapsules (NEMs) with smooth surface, good sphericity, excellent dispersivity and uniform particle size distribution were prepared by emulsification combined with electrospraying to extend the sustained release performance of the embolic microcapsules loading capecitabine (CAP). The sodium alginate and chitosan with good biocompatibility were used as the materials and CAP as a small-molecule model drug. The drug loading, encapsulation efficiency and drug release of CAP in the NEMs were investigated. The results showed that the drug-loading and encapsulation efficiency both increased with the increment of chitosan and CAP concentration. The maximum values of drug loading and encapsulation efficiency were 1.97 and 18.01 % respectively when initial CAP concentration was 5.0 g/L and chitosan molecular weight 100 kDa. The cumulative release rate of CAP released from the NEMs was lower than 30 % in 0.5 h, which indicated that there was no obvious initial burst release behavior. In the subsequent 240 h, the release results confirmed that the NEMs had better sustained release properties compared to pure microcapsules, and it might be a new anticancer drug delivery system in the future studies.

Enhanced oral bioavailability of paclitaxel in pluronic/LHR mixed polymeric micelles: preparation, in vitro and in vivo evaluation

In order to enhance paclitaxel oral bioavailability, mixed polymeric micelles that comprised of pluronic copolymers and low molecular weight heparin-all-trans-retinoid acid (LHR) conjugate were developed. PTX-loaded mixed polymeric micelles (MPMs) were prepared by dialysis method with high drug loading 26.92 ± 2.08% and 25.82 ± 1.9% for F127/LHR and P188/LHR MPMs respectively, and were found to be spherical in shape with an average size of around 140 nm and a narrow size distribution. In vitro release study showed that pluronic/LHR MPMs exhibited delayed release characteristics compared to Taxol and faster drug release profile compared to LHR plain polymeric micelles (PPMs). The cytotoxic activity of PTX-loaded pluronic/LHR MPMs was slightly higher than LHR PPMs in MCF-7 cells (p<0.01). In situ effective permeability of PTX through rat small intestine was 5- to 6-fold higher with mixed micelles than that of Taxol. Moreover, pluronic/LHR MPMs achieved significantly higher AUC and C(max) level than both of LHR PPMs and Taxol. This enhancement might be due to the inhibition of both P-glycoprotein efflux system and cytochrome P450 metabolism by pluronic copolymers. The current results encourage further development of paclitaxel mixed polymeric micelles as an oral drug delivery system.

Facile fabrication of biocompatible PLGA drug-carrying microspheres by O/W pickering emulsions

This study is focused on the preparation of Ibuprofen (IBU) loaded micrometer-sized poly(lactic-co-glycolic acid) (PLGA) microspheres and process variables on the size, drug loading and release during preparation of formulation. Silicon dioxide (SiO(2)) nanoparticle-coated PLGA microspheres were fabricated via a combined system of "Pickering-type" emulsion route and solvent volatilization method in the absence of any molecular surfactants. Stable oil-in-water emulsions were prepared using SiO(2) nanoparticles as a particulate emulsifier and a dichloromethane (CH(2)Cl(2)) solution of PLGA as an oil phase. The SiO(2) nanoparticle-coated PLGA microspheres were fabricated by the evaporation of CH(2)Cl(2) in situ, and then bare-PLGA microspheres were prepared by removal of the SiO(2) nanoparticles using HF aqueous solution. The two types of microspheres were characterized in terms of size, component and morphology using scanning electronic microscope (SEM), Fourier-transform infrared, optical microscope, and so on. Moreover, IBU was encapsulated into the hybrid beads by dispersing them in the CH(2)Cl(2) solution of PLGA in the fabrication process. The sustained release could be obtained due to the barrier of the polymeric matrix (PLGA). More over, the release curves were nicely fitted by the Weibull equation and the release followed Fickian diffusion. The combined system of Pickering emulsion and solvent volatilization opens up a new route to fabricate a variety of microspheres. The resulting microspheres may find applications as delivery vehicles for biomolecules, drugs, cosmetics and living cells.